The present invention relates to data processing systems and particularly to systems having two or more programmed data processing machines which are interconnected.
The architectures of data processing systems are in part controlled by the technology utilized to build the circuits. New semiconductor technologies have allowed larger and larger parts of systems to be integrated into smaller and smaller packages. Modular systems, distributed-function systems, and other types of new systems are becoming common. One example of a new system is described in the above cross-referenced application entitled CONTROLLER FOR DIGITAL DEVICES where a programmable data processing machine functions as a controller for an input/output user device.
Controllers in general connect over input/output interfaces to one or more controlled input/output devices. The controllers function to produce output signals to the devices which are a function, in part, of input signals from the devices. The controllers desirably produce the output signals, after receiving input signals, in as short a time as possible. The number of and logical states of input and output signals to and from controllers vary widely for different controlled devices. For example, a controller for controlling a magnetic disc unit requires different signals than a controller for controlling a Teletype terminal. The controller in the above cross-referenced application can be utilized with many different types of controlled devices merely by changing the program within the controller.
When data processing machines, such as the programmed controller in the cross-referenced application are to be tested or utilized with other machines, the machines must be connected together. A need exists, therefore, for improved methods and apparatus to interconnect one data processing machine, having one stored program of instruction, with other data processing machines having other stored programs of instructions.
In accordance with the above background, an object of the present invention is to provide an improved data processing system in which two or more programmed data processing machines are interconnected.